It is known that after congenital malformations or anomalies, or even after fractures, losses of osseous or other substances, certain bones such as the humerus, femur, tibia, atc., are too short, thus creating asymmetry or hypometry. In the case of lower limbs with slight asymmetry, less than 3 centimeters, orthopedic treatment is called for by adding, for example, a shoe or other orthopedic apparatus to the limb which is short. With asymmetry or hypometry which is more significant, in order to elongate the shorter limb, surgical solutions currently using two types of means exist:
External fixtures--an operation is made using external apparatus on certain parts of which, for example, metal pins, etc., go through the soft tissues to reach the bone of which they are an integral part. The apparatus can be seen from outside the limb. The advantage of such apparatus which is therefore accessible fron outside of the limb, is to be able to act on the apparatus at determined periods of time in order to consequently provoke a certain degree of elongation of the bone in a progressive manner generally at the diaphysis of the bone after cutting the latter. However, problems regarding attractiveness are encountered as the user has difficulties in putting up with such apparatus and risks of infection are not negligible; and
Internal fixtures: the second solution consists of taking action from the inside, i.e., no element can be seen from outside the limb. For this purpose, centro-medullar nails or intramedullary nails are generally used or osteosynthesis plates which are suitably fixed to the bone.
The advantage of this solution with respect to the previous one, lies in the fact that no element can be seen from outside the limb. On the other hand, the bone cannot be progressively elongated. However, a quite significant elongation can be carried out thanks to repeated surgical interventions which are consistent each time in obtaining a fixed but limited elongation due to elastic and plastic limits of the soft tissues on stretching. In the case of non-progressive significant elongation, the compensation of the dimensional deviation is risky and requires adjuvants to the osteosynthesis, e.g. grafts, etc., which reduce the mechanical and physiological properties of the elongated bone.
No strictly internal fixing system, fully imbedded into the patient, currently exists which enables a limb to be elongated progressively with a mechanism incorporated into the fixing system, either automatically moved or moved by external action on the limb.